Many electronic systems use a clock signal that is provided to the components of the electronic system. Ideally, a single clock frequency is created by a clock generation circuit and provided, via the clock signal, to the components.
With the rise in use of mobile devices, power has become an important concern. Manufacturers of electronic systems have tried to increase performance as well as extend battery life. Even non-mobile devices have been designed to use less power, particularly during idle times.
One technique used to save power is to have clock generation circuits capable of producing multiple clock frequencies. However, many clock generation circuits can become unstable during transitions between clock frequencies. Consequently, the clock signal of such a clock generation circuit is generally turned off for a certain time period after a transition between clock frequencies. The time period is chosen to ensure that the clock generation circuit has transitioned to a new frequency and has a stable output. During this time period, the electronic system is essentially frozen, as nothing will be input to or output from the system.
Nonetheless, the above technique allows clock frequency in the electronic system to be increased or decreased. During a need for high speed operation, such as during normal use of the electronic system, the clock frequency is increased, generally to about a maximum frequency. During idle times or at other times where high speed operation is not necessary, the clock frequency is decreased, generally to a speed conducive for lower power.
Although techniques exist for changing clock frequency in an electronic system, a need still exists for techniques that can more smoothly change clock frequency.